I see mathematics as structures made up of numbers & shapes and actions done with them, like additions-multiplications-exponentiations, or divisions in pieces, translations, rotations, or some other changes of shape.
I'm exploring whether something substantial can be said in general, e.g. about “addition”, “multiplication”, the “distributive law” and “exponentiation”, in a broad philosophical outlook,
(for example, one could argue that adding is simple amassing, while multiplying is structuring the collected pieces in geometrical forms),
that would provide some clues to a unified understanding of pre-19th century algebra, geometry, calculus & complex variables, and motivate their further study, possibly some books on general axiomatic theories (groups, sets, topology, categories…) with historical accounts and many concrete examples.